Fault detection system for actuator

Patent metadata

Field	Value
Publication number	US-9891135-B2
Application number	US-201414313199-A
Country	US
Kind code	B2
Filing date	Jun 24, 2014
Priority date	Jul 8, 2013
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

A failure detecting device of a fault detection system includes a detection time calculator, which calculates a stroke time T3 required for a piston to travel between one end and another end of an actuator based on detection signals from a first sensor and a second sensor, a statistical processor that performs a predetermined statistical calculation with respect to the stroke time T3, and a fault response detector, which detects whether or not a fault of the actuator has occurred based on a processing result of the statistical processor.

First claim

What is claimed is:

1. A fault detection system for an actuator having one end and an other end, based on a stroke time of a movable member of the actuator, comprising:
a first sensor disposed on the one end of the actuator along a displacement direction of the movable member, and which detects the movable member upon displacement thereof from the other end to the one end;
a second sensor disposed on the other end of the actuator along the displacement direction, and which detects the movable member upon displacement thereof from the one end to the other end;
a fault detecting device that judges a fault on the one end side or the other end side of the actuator based on detection results of the first sensor and the second sensor;
a directional switching valve that selectively supplies a pressure fluid to the one end or the other end of the actuator, based on an external control signal supplied thereto;
a first tube that connects the directional switching valve and the one end of the actuator and supplies the pressure fluid to the one end; and
a second tube that connects the directional switching valve and the other end of the actuator and supplies the pressure fluid to the other end;
wherein the fault detecting device further comprises:
a stroke time calculator which calculates, as a stroke time required for the movable member to travel between the one end and the other end, a time difference between a first detection time from start of supply of the control signal to the directional switching valve until a time at which the movable member can no longer be detected by one of the first sensor and the second sensor, and a second detection time from the start of supply until a time at which detection of the movable member by the other of the first sensor and the second sensor is started, when the movable member is displaced in the displacement direction in accordance with the selective supply of the pressure fluid from the directional switching valve to the one end of the actuator via the first tube or from the directional switching valve to the other end of the actuator via the second tube;
a statistical computation processing unit that performs a predetermined statistical calculation with respect to one of the stroke time, the first detection time or the second detection time; and
a fault detector which judges whether or not the fault on the one end side or the other end side has occurred, based on a processing result of the statistical computation processing unit,
wherein when the statistical computation processing unit performs the predetermined statistical calculation with respect to the first detection time, the fault detector judges, based on a result of the predetermined statistical calculation with respect to the first detection time, whether the fault has occurred on the one end side or the other end side of the actuator.

2. The fault detection system according to claim 1 , the fault detecting device further including a first storage unit in which one of the stroke time, the first detection time or the second detection time is stored, and a second storage unit in which the processing result is stored,
wherein the fault detector reads out the processing result that is stored in the second storage unit, and judges whether or not the fault has occurred based on the read out processing result.

3. The fault detection system according to claim 2 , wherein:
a normal stroke time of the movable member is stored beforehand as a normal value in the first storage unit;
the statistical computation processing unit calculates at least a deviation between the stroke time calculated by the stroke time calculator and the normal value, and stores the calculated deviation as a statistically calculated value in the second storage unit; and
the fault detector reads out the statistically calculated value from the second storage unit, and judges whether or not the fault has occurred based on the read out statistically calculated value.

4. The fault detection system according to claim 2 , wherein:
in a case that the first sensor and the second sensor detect the movable member each time that the movable member moves in the displacement direction, the stroke time calculator calculates and stores the stroke time in the first storage unit each time that respective detection results from the first sensor and the second sensor are input;
each time that the stroke time calculator calculates and stores the stroke time in the first storage unit, the statistical computation processing unit reads out data of all of the stroke times that are stored in the first storage unit, calculates an average value, a standard deviation, or a variance of the read out data, and stores the average value, the standard deviation, or the variance as a statistically calculated value in the second storage unit;
an average value, a standard deviation, or a variance of a normal stroke time of the movable member is stored as a normal value in the second storage unit; and
each time that the statistical computation processing unit stores the statistically calculated value in the second storage unit, the fault detector reads out the statistically calculated value and the normal value from the second storage unit, and judges whether or not the fault has occurred based on a comparison between the statistically calculated value and the normal value.

5. The fault detection system according to claim 4 , wherein:
in a case that the movable member is moved reciprocally along the displacement direction at a fixed time period from an initial state of operation of the actuator, the stroke time calculator calculates the stroke time of the movable member and stores the calculated stroke time in the first storage unit, each time that respective detection results from the first sensor and the second sensor are input; and
the statistical computation processing unit reads out the data of all of the stroke times that are stored in the first storage unit, calculates an average value, a standard deviation, or a variance of the read out data, and stores the average value, the standard deviation, or the variance as a normal value in the second storage unit.

6. The fault detection system according to claim 2 , wherein:
the stroke time calculator stores the first detection time, the second detection time, and the stroke time in the first storage unit;
the statistical computation processing unit performs a predetermined statistical calculation with respect to the first detection time, and stores a processing result of the statistical calculation in the second storage unit; and
the fault detector reads out the processing result with respect to the first detection time that is stored in the second storage unit, and based on the read out processing result, judges whether or not the fault has occurred on the one end side or the other end side of the actuator.

7. The fault detection system according to claim 6 , further comprising a controller that supplies the control signal to the directional switching valve,
wherein the fault detecting device further includes an output processor that supplies the control signal from the controller to the directional switching valve, and outputs the detection result of the fault detector to the controller.

8. The fault detection system according to claim 2 , further comprising a display device that displays one of the stroke time, the detection time or the second detection time stored in the first storage unit, the processing result stored in the second storage unit, and the detection result of the fault detector.

9. A fault detection system configured to detect a fault based on a stroke time of a movable member of the actuator, comprising:
a first sensor dispose

Assignees

• Smc Corp

Inventors

• Aki Tomohiko

Classifications

• F15B2211/857

  Monitoring of fluid pressure systems · CPC title

• F15B19/005 Primary

  Fault detection or monitoring · CPC title

• F15B2211/7653

  at distinct positions, e.g. at the end position · CPC title

• F15B15/2815

  Position sensing, i.e. means for continuous measurement of position, e.g. LVDT · CPC title

• F15B2211/864

  Failure of an output member, e.g. actuator or motor failure · CPC title